Many mammals, including apes, monkeys, squirrels, bears, kangaroos, and even ground sloths, engage in forms of facultative bipedalism. Humans walk on two legs, known as bipedality, which is unique to humans Other mammals, like dogs and cats, walk on all four legs, known as quadrupedalism Some animals can stand or walk on two legs for a short time, and some birds are bipeds Only humans and primates regularly walk on two legs. To define humans categorically as “bipedal” is not enough
To describe them as habitually bipedal is nearer the truth, but habit as such does not leave its mark on fossil bones. Evolution works with what it has, and the bipedal human body remains a compromise Perhaps the greatest cost was the restructuring of the birth canal A wider pelvis was needed for balance, but a narrower one made childbirth more difficult At the same time, the human brain was growing larger. But the most recent findings show that bipedalism occurred very early in our history, before the savannahs appeared
